1. Field of the Invention
This invention relates to the field of wireless network systems, and relay terminals and programs in the wireless network systems, in which an information transmission source terminal broadcasts data, and in which relay terminals relay in multiple stages and distribute data to peripheral terminal devices.
Priority is claimed on Japanese Patent Application No. 2004-55227, filed Feb. 27, 2004, the content of which is incorporated herein by reference.
2. Description of Related Art
In the wireless network system, a technique called “flooding” is applied to notify receipt of broadcasted packets. “Flooding” is a technique to distribute data to terminals distributed around an information transmission source terminal. The information transmission source terminal transfers (broadcasts) the broadcast packet and all the terminals that receive it broadcast it. The process is repeated. In other words, when processing a flooding, data is transferred to terminals located in all the directions.
On the other hand, for the purpose of reducing the number of terminal equipment to relay, “the information transmission method, the information transmission system, the information terminal, and the information memory medium” (for example, in Japanese Patent Application, Unexamined Publication No. 2001-339399) have been proposed. In this proposal, terminals relay the data only when the current information direction vector and the current direction vector show the same direction. The current information direction vector shows the movement of the data from the information transmission source terminal to the reply terminal. The current direction vector shows the movement direction of the relay terminal. However, the method transfers the data in all the directions.
In some cases, the data can be effective only for the terminals in some directions and some positions. In this case, the data cannot be useful in other directions and other positions. Transferring such data to all directions wastes electric power and resources for wireless terminals.
For example, in the case of a multi-hop radio network, formed among cars, informs about the approach of the emergency vehicle. Information has importance for cars in the area where an emergency vehicle will pass by shortly. With the conventional technique, notifying information in all directions, wireless terminals, behind the emergency vehicle, might waste resources. Also, in notification of traffic accident information, the information is meaningful for cars which head for the place where the accident occurred. That is why, for example, on a one-way road, it can also be a waste of the wireless terminal resources.